Everbilt anti-siphon frost proof Sillcock assure protection against freezing and undesirable back siphoning. Because they're frost proof, they can stop outside hydrants from freezing and bursting the pipes. Plus, the anti-siphon feature protects against water siphoning back to contaminate the potable water system. Also, unlike anti-siphon attachments, which must be manually drained to prevent freezing, the integral anti-siphon design is self-draining.Durable brass constructionBuilt-in vacuum breaker eliminates back flow3/4 in. MIP or 1/2 in. FIP inlet connection3/4 in. hose thread outlet fits most 3/4 in. garden hosesIntegrated flange designed to cover the hole into the home Proposition 65 Information WARNING: This product can expose you to chemicals including Lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.